Pressure sensors on flexible substrates for stress decoupling

ABSTRACT

A semiconductor device includes a semiconductor chip including a chip substrate and a MEMS element, wherein the chip substrate includes a first surface and a second surface arranged opposite to the first surface, and wherein the MEMS element is disposed at the first surface of the chip substrate and the MEMS element includes a sensitive area; at least one electrical interconnect structure electrically connected to the first surface of the chip substrate; a chip carrier electrically connected to the at least one electrical interconnect structure; a flexible film provided over the second surface of the chip substrate to form a pocket in which the semiconductor chip resides; and a compressible material arranged between the second surface of the chip substrate and the flexible film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/143,332 filed on Jan. 7, 2021, which is a continuation of U.S. patentapplication Ser. No. 16/910,595 filed on Jun. 24, 2020, now U.S. Pat.No. 10,910,283 issued Feb. 2, 2021, which is a continuation of U.S.patent application Ser. No. 16/294,208 filed Mar. 6, 2019, now U.S. Pat.No. 10,777,474 issued Sep. 15, 2020, which are incorporated by referenceas if fully set forth.

FIELD

The present disclosure relates generally to semiconductor devices and amethod of manufacturing the same, and, more particularly,microelectromechanical systems (MEMS) elements with a stress reliefmechanism.

BACKGROUND

Microelectromechanical system (MEMS) are microscopic devices,particularly those with moving parts. MEMS became practical once theycould be fabricated using modified semiconductor device fabricationtechnologies, normally used to make electronics. Thus, a MEMS may bebuilt into a substrate as a component of an integrated circuit, that isdiced into a semiconductor chip that is subsequently mounted in apackage.

Mechanical stress and other external mechanical influences introduced toa package may inadvertently be transferred through the package to anintegrated MEMS element, such as sensor, and, more particularly, to apressure sensor. This transferred mechanical stress may affect theoperation of the MEMS element or induce an shift (e.g., an offset) in asensor signal that may lead to incorrect measurements.

For example, semiconductor pressure sensors have a pressure sensitiveelement arranged to measure an absolute pressure or a relative pressure(e.g. the difference between two pressures). A problem with manypressure sensors is that the sensor measures (or outputs, or gives) asignal, even in the absence of a pressure (or pressure difference) to bemeasured. This offset may be the result of mechanical stress and/ordeformation of the housing (e.g., the packaging) of the sensor. Thehousing-stress/deformation will typically also cause a stress-componentat the sensor surface where the sensitive elements (e.g.,piezo-resistors) are located, and thereby cause an offset error, alinearity error, or even a hysteresis error to the output signal.

Therefore, an improved device capable of decoupling mechanical stressfrom an integrated MEMS element may be desirable.

SUMMARY

One or more embodiments provide a semiconductor device that includes asemiconductor chip including a substrate having a first surface and asecond surface arranged opposite to the first surface; and amicroelectromechanical systems (MEMS) element, including a sensitivearea, disposed at the first surface of the substrate. The semiconductordevice further includes at least one electrical interconnect structureelectrically connected to the first surface of the substrate, and aflexible carrier electrically connected to the at least one electricalinterconnect structure, where the flexible carrier wraps around thesemiconductor chip and extends over the second surface of the substratesuch that a folded cavity is formed around the semiconductor chip.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described herein making reference to the appendeddrawings.

FIG. 1 shows a cross-sectional diagram of a pressure sensor packageaccording to one or more embodiments;

FIGS. 2A-2C show a cross-sectional diagram of a pressure sensor packageaccording to one or more embodiments;

FIG. 3 shows a cross-sectional diagram of a pressure sensor packageaccording to one or more embodiments;

FIG. 4 shows a cross-sectional diagram of a pressure sensor packageaccording to one or more embodiments;

FIG. 5 shows a cross-sectional diagram of a pressure sensor packageaccording to one or more embodiments;

FIG. 6 shows a top view of the pressure sensor package shown in FIG. 1;and

FIG. 7 shows a top view of the pressure sensor package according to oneor more embodiments.

DETAILED DESCRIPTION

In the following, various embodiments will be described in detailreferring to the attached drawings, where like reference numerals referto like elements throughout. It should be noted that these embodimentsserve illustrative purposes only and are not to be construed aslimiting. For example, while embodiments may be described as comprisinga plurality of features or elements, this is not to be construed asindicating that all these features or elements are needed forimplementing embodiments. Instead, in other embodiments, some of thefeatures or elements may be omitted, or may be replaced by alternativefeatures or elements. Additionally, further features or elements inaddition to the ones explicitly shown and described may be provided, forexample conventional components of sensor devices.

Features from different embodiments may be combined to form furtherembodiments, unless specifically noted otherwise. Variations ormodifications described with respect to one of the embodiments may alsobe applicable to other embodiments. In some instances, well-knownstructures and devices are shown in block diagram form rather than indetail in order to avoid obscuring the embodiments.

Further, equivalent or like elements or elements with equivalent or likefunctionality are denoted in the following description with equivalentor like reference numerals. As the same or functionally equivalentelements are given the same reference numbers in the figures, a repeateddescription for elements provided with the same reference numbers may beomitted. Hence, descriptions provided for elements having the same orlike reference numbers are mutually exchangeable.

In this regard, directional terminology, such as “top”, “bottom”,“front”, “behind”, “back”, “leading”, “trailing”, “below”, “above” etc.,may be used with reference to the orientation of the figures beingdescribed. Because parts of embodiments can be positioned in a number ofdifferent orientations, the directional terminology is used for purposesof illustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope defined by the claims. Thefollowing detailed description, therefore, is not to be taken in alimiting sense.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

In embodiments described herein or shown in the drawings, any directelectrical connection or coupling, i.e., any connection or couplingwithout additional intervening elements, may also be implemented by anindirect connection or coupling, i.e., a connection or coupling with oneor more additional intervening elements, or vice versa, as long as thegeneral purpose of the connection or coupling, for example, to transmita certain kind of signal or to transmit a certain kind of information,is essentially maintained. Features from different embodiments may becombined to form further embodiments. For example, variations ormodifications described with respect to one of the embodiments may alsobe applicable to other embodiments unless noted to the contrary.

The term “substantially” may be used herein to account for smallmanufacturing tolerances (e.g., within 5%) that are deemed acceptable inthe industry without departing from the aspects of the embodimentsdescribed herein.

Embodiments relate to microelectromechanical system (MEMS), andparticularly to MEMS pressure sensors, integrated on a semiconductorchip and subsequently mounted to a package. The MEMS may be referred toas a MEMS element, a MEMS cell, or a MEMS device. The side or surface ofthe chip at which the MEMS element is provided may be referred to as afront side or front surface of the chip, whereas the side or surface ofthe chip opposite thereto may be referred to as a back side or a backsurface of the chip.

The package is adapted to enable the MEMS pressure sensor to detectand/or measure a force imposed thereon. For example, the MEMS pressuresensor may operate as a transducer that generates an electrical signalas a function of the pressure imposed, and the package may have anopening formed in proximity to the MEMS pressure sensor that allows amedium to interact with the MEMS pressure sensor. The medium may be anypressure measurable or pressure inducing entity.

In general, a sensor, as used herein, may refer to a component whichconverts a physical quantity to be measured to an electric signal, forexample a current signal or a voltage signal. The physical quantity may,for example, be pressure as an expression of force imposed on asensitive area or region of the sensor. Chemicals, humidify, and debris,such as foreign particles, may negatively impact the performance of anysensor. Thus, it is desirable to prevent these and other potentialcontaminants from reaching the surface of the sensor, and, specifically,from reaching the sensitive area or region of the sensor.

A manufacturing process for semiconductor chip fabrication may includetwo sequential sub-processes commonly referred to as front-end andback-end production. The back-end production may further include twosequential sub-processes commonly referred to as pre-assembly andassembly.

Front-end production refers primarily to wafer fabrication. A wafer, asused herein, may also be referred to as a substrate. The front-endproduction may start with a clean disc-shaped silicon wafer that willultimately become many silicon chips. First, a photomask that definesthe circuit patterns for circuit elements (e.g., transistors) andinterconnect layers may be created. This mask may then be laid on theclean silicon wafer and is used to map the circuit design. Transistorsand other circuit elements may then be formed on the wafer throughphotolithography. Photolithography involves a series of steps in which aphotosensitive material is deposited on the wafer and exposed to lightthrough a patterned mask; unwanted exposed material is then etched away,leaving only the desired circuit pattern on the wafer. By stacking thevarious patterns, individual elements of the semiconductor chip may bedefined. A MEMS device or MEMS element may also be incorporated ontoand/or into the surface of the wafer and connected to one or morecircuit elements. During the final phase of the front-end productionprocess, each individual chip on the wafer is electrically tested toidentify properly functioning chips for assembly.

Back-end production refers to the assembly and test of individualsemiconductor devices or chips. The assembly process is intended toprotect the chip, facilitate its integration into electronic systems,limit electrical interference and enable the dissipation of heat fromthe device. Once the front-end production process is complete, the waferis sawed or diced into individual semiconductor chips. This dicing ofthe wafer into individual semiconductor chips is referred to aspre-assembly.

In an assembly phase of the back-end production, the semiconductor chipsare incorporated into a package. For example, these semiconductor chipsmay be individually attached by means of an alloy or an adhesive to alead frame, a metallic device used to connect the semiconductor to acircuit board. Leads on the lead frame may then be connected by aluminumor gold wires to the input/output terminals on the semiconductor chipthrough the use of automated machines known as wire bonders. Eachsemiconductor device may then be at least partially encapsulated in aplastic molding compound or a ceramic case, forming the package.

Thus, a MEMS element may be built into a substrate as a component of anintegrated circuit, the substrate then being diced into semiconductorchips that are each subsequently mounted in a package.

It will be appreciated that while the pre-assembly (i.e., dicing)process may be described as part of the back-end production flow, thechips may be partially singulated during final phase of the front-endproduction. Thus, in some instances, pre-assembly may begin or may beperformed during the front-end production.

According to one or more embodiments, mechanical stress-decoupling isprovided to a MEMS element as a stress relief mechanism. Astress-decoupling feature such as one or more trenches (i.e., one ormore stress-decoupling trenches) may be provided. In additionally, eachstress-decoupling trench is filled with a gel (e.g., a silicone gel) andthe gel may additionally be deposited on the MEMS element at the waferlevel (i.e., during the front-end production process), or during orsubsequent to the pre-assembly process, but prior to assembly (i.e.,packaging). The protective material may be deposited on an exposedsurface of the MEMS element such that an entire exposed surface of theMEMS element is covered by the protective material.

The exposed surface of the MEMS element may include or may be referredto as a sensitive area that enables the MEMS element to measure aphysical quantity. For example, the MEMS element may be a MEMS pressuresensor that is configured to detect or measure a change in pressure inresponse to a change of force imposed on the exposed surface. Theprotective material is configured such that, when the MEMS element iscovered by the protective material, a sensor functionality of the MEMSelement remains intact. For example, the protective material may be asilicone gel that has a viscosity that permits a force exerted thereonto be transferred to the MEMS pressure sensor. Thus, the protectivematerial is flexible enough that when the protective material isdepressed, the sensitive area of the MEMS pressure sensor is alsodepressed proportionally.

More particularly, the protective material permits full sensorfunctionality of the MEMS element, including mechanical functionalityand electrical functionality, while sealing an entire surface of theMEMS element. Even more particularly, the protective material isconfigured such that no functionality of the MEMS element is impeded bythe protective material.

By ensuring that the functionality of the MEMS element remains intact,the protective material may be deposited onto the MEMS element as apermanent material at an early stage of the chip fabrication process.Thus, the MEMS element may already be configured in an operable state(e.g., a final operable state) at the time the protective material isdeposited onto the MEMS element, and the protective material may remaincompletely intact after deposition, including throughout the assemblyprocess, such that it remains a feature in the final product.

As a result of the early deposition of the protective material, the MEMSelement is provided early particle and humidity protection from foreignmatter that may have been introduced during (pre-)assembly processesthat could influence the sensor performance.

While some embodiments provided herein may refer to the protectivematerial as being silicone gel, the protective material is not limitedthereto, and may be any material that provides protection from foreignmatter while permitting sensor functionality of the MEMS element, andmore particularly permits sensor functionality of the MEMS element atthe time of deposition of the protective material. Thus, the protectivematerial may be any material that behaves like a fluid in order totransfer applied pressure to a sensitive membrane of a pressure sensor.

Embodiments include a silicon die on which an MEMS element isintegrated, where the silicon die has sufficiently low stress on theMEMS element. The silicon die can be a bare die or a chip size package(CSP) mounted on a flexible carrier that minimizes or prohibits thetransfer of mechanical stress to the silicon die, and ultimately to theMEMS element, due to its low mechanical stiffness. The flexible carriercan be a foil printed circuit board (PCB) or a normal PCB with stressrelieve structures, such as stress decoupling trenches, that enable thenormal PCB to be flexible. Environmental protection is performed by acombination of a protective material (e.g., silicone gel) disposedaround the MEMS element with the flexible carrier.

FIG. 1 shows a cross-sectional diagram of a pressure sensor package 100according to one or more embodiments. The pressure sensor package 100includes chip 1 bonded to a flexible carrier 2 by bonding balls 3. Thechip 1 may be a bare die or a CSP. Thus, no molding is applied to thepackage 100 (e.g., to encapsulate the chip). The flexible carrier 2 maybe a foil PCB or a normal PCB with stress relieve structures, such asstress decoupling trenches, that enable the normal PCB to be flexible.Thus, the flexible carrier 2 may be referred to as a stress decouplingcarrier or substrate. Furthermore, while bonding balls are used in thedescribed examples, it will be appreciated that any electricalinterconnect structure may be used to provide contact between the chip 1and the flexible carrier 2.

The chip 1 is an integrated circuit (IC) that includes a semiconductorsubstrate 10 (e.g., a silicon substrate) having a main surface 11 on thefront side of the chip 1 and a MEMS element 12 provided at the mainsurface 11. The main surface 11 may be referred to as an active chipsurface that includes additional circuitry that interfaces with the MEMSelement 12. The bonding balls 3 are coupled to a pad on the main surface11 of the chip 1 and to the flexible carrier 2, and is used for carryingelectrical signals therebetween. In this arrangement, the chip 1 isassembled face down on the flexible carrier 2 such that a sensitive areaof the MEMS element 12 faces towards the flexible carrier.

The MEMS element 12 is a pressure sensor arranged at the main surface 11such that the MEMS element 12 is capable of sensing a change in pressureapplied thereto. Thus, the MEMS element 12 includes a sensitive areathat either protrudes from the main surface 11 and/or is located in anopening of the main surface 11 in which the sensitive area resides. TheMEMS may also utilize a backside processing of the silicon die (e.g.,bulk micro machining or die bonding with other wafers).

The pressure sensor package 100 further includes a flexible protectivematerial 13, such as silicone gel, disposed and coupled between the MEMSelement 12 and the flexible carrier 2. The flexible protective material13 may be placed such that an entire exposed surface of the MEMS element12, including the sensitive area, is encapsulated by the flexibleprotective material 13. Thus, the flexible protective material 13 isplaced at least in the region where the MEMS element 12 is located, andthe flexible protective material 13 is used to fill the gap the MEMSelement 12 and the flexible carrier 2. By this arrangement, pressure maybe applied to the flexible carrier 2 such that it is transferred throughthe flexible protective material 13 to the MEMS element 12.Additionally, pressure applied directly to the protective material 13 istransferred through the flexible protective material 13 to the MEMSelement 12, such that the flexible carrier 2 does not influence themeasurement. This direct application of pressure to the protectivematerial 13 may be achieved at one or more of the slits or openings 19that extend through the flexible carrier 2, or at any other region wherethe protective material 13 is exposed to the ambient.

As shown, the flexible protective material 13 is further bonded to atleast a portion of the main surface 11 of the chip 1. Thus, the flexibleprotective material 13 completely fills the gap between the main surface11, including the MEMS element 12, and the flexible carrier 2.

The flexible carrier 2 may also include a plurality of slits or openings19 that may increase the flexibility of the carrier 2 and also reducethe amount of mechanical stress transferred to the inner region of thecarrier where the MEMS element is bonded thereto. For example, the slits19 may be located in proximity of the bonding balls 3. In some cases,the slits 19 may surround a periphery of the bonding balls 3 in acircular pattern.

FIGS. 2A-2C show a cross-sectional diagram of a pressure sensor package200 according to one or more embodiments. Similar to the pressure sensorpackage 100 shown in FIG. 1, the pressure sensor package 200 includeschip 1 bonded to a flexible carrier 2 by bonding balls 3, with theexception that the flexible carrier 2 is folded around the chip 1 foradditional protection. By folding the flexible carrier 2 around the chip1, a folded pocket 21 or cavity is formed around the chip 1. Thus, theflexible carrier 2 encircles at least three sides of the chip 1,including the main surface 11, a back surface 14 opposite to the mainsurface 11, and a side surface 15 that adjoins the main surface 11 andthe back surface 14.

As shown in FIG. 2B, the folded pocket 21 is at least partially filledwith a compressible foam 22 such that a gap between the back surface 14and the flexible carrier 2 is filled with the foam 22 and such that agap between the side surface 15 and the flexible carrier 2 is filledwith the foam 22. At the very least, the foam 22 should be porous inorder for it to forward pressure unchanged to the protective material 13and be detected by the pressure sensor. The foam 22 may be pressed intothe folded pocket 21 for protection and media filtering.

Alternatively, a soft tissue or a mesh of fibers could be used insteadof a foam. Thus, any material that is compressible and porous may beused in place of foam 22. This material may be referred to as a fillingmaterial that is compressible and porous that is configured to forwardpressure unchanged to the protective material 13.

In addition, the foam 22 may cover another side surface 16 of the chip 1such that the foam 22 encapsulates the chip 1 on all remaining sides ofthe chip 1, with the exception of the main surface 11. As describedabove, the flexible protective material 13 is used to fill the gap themain surface 11, including the MEMS element 12, and the flexible carrier2.

Thus, in one example, the flexible carrier 2 may first be folded over toform the folded pocket 21, and then foam 22 may be injected into thefolded pocket 21 to fill the remaining gaps and seal the chip 1, bondingballs 3, and the MEMS element 12.

Alternatively, the foam 22 may be disposed on the chip 1 to encapsulatethe exposed surfaces of the chip 1, and then the flexible carrier 2 maybe folded over the dispensed foam 22 to form the structure shown in FIG.2B.

As another alternative, the foam 22 may be glued to the flexible carrier2 before being folded over the chip 1. Once glued, the flexible carrier2 and the foam 22 may be folded over the chip 1 to achieve the sameresult depicted in FIG. 2B.

The flexible carrier 2 may further include one or more pressure openings34 that extend through the portion of the flexible carrier 2 that isfolded over the backside of the chip 1. The pressure openings 34 allowthe flexible carrier 2 to be porous so that air pressure can passtherethrough. Thus, the pressure openings 34 serve to dissipatemechanical stress.

As shown in FIG. 2C, the folded pocket 21 is filled with the flexibleprotective material 13 in an area that entirely encapsulates the chip 1,including the MEMS element 12. The compressible foam 22 may be furtherdispensed at a side region of the package 200 to enclose the chip 1 andthe flexible protective material 13 within the folded pocket 21. That isa remaining portion of the folded pocket 21 is filled with the foam 22.

Thus, in one example, the flexible carrier 2 may first be folded over toform the folded pocket 21, and then the flexible protective material 13may be injected into the folded pocket 21 to fill the remaining gaps andseal the chip 1, bonding balls 3, and the MEMS element 12. Subsequently,the foam 22 may then be injected to seal the flexible protectivematerial 13 inside the folded pocket 21.

While not shown, the flexible carrier 2 in FIGS. 2A-2C may furtherinclude slits similar to slits 19 shown in FIG. 1.

Alternatively, the flexible protective material 13 may be disposed onthe chip 1 to encapsulate the exposed surfaces of the chip 1, and thenthe flexible carrier 2 may be folded over the dispensed flexibleprotective material 13 to form the structure shown in FIG. 2C.Subsequently, the foam 22 may then be injected to seal the flexibleprotective material 13 inside the folded pocket 21.

FIG. 3 shows a cross-sectional diagram of a pressure sensor package 300according to one or more embodiments. Similar to the pressure sensorpackages 100 and 200 shown in FIGS. 1 and 2A-2C, the pressure sensorpackage 300 includes chip 1 bonded to a flexible carrier 2 by bondingballs 3, with the exception that a flexible film sticker 31 is providedover the back side of the chip 1 to form a pocket 32 or cavity in whichthe chip 1 resides.

In particular, the film sticker 31 may be bonded to the flexible carrier2 at a perimeter that surrounds the chip 1. Thus, the film sticker 31extends from a bonded area of the flexible carrier 2 over a back side ofthe chip 1. A compressible foam 22 may then be injected between aninside surface of the film sticker 31 and the chip 1 such that the foam22 separates the film sticker 31 from the chip 1. As a result, thepocket 32 is formed or is enlarged by the injection of the foam 22.

Alternatively, the foam 22 may be first disposed on the chip 1 and theflexible carrier 2 to encapsulate the exposed surfaces of the chip 1,and then the film sticker 31 may be placed over the foam 22 and bondedto the flexible carrier 2.

As another alternative, the foam 22 may be glued to the film sticker 31and then glued over the chip 1. Thus, the film sticker 31 may be gluedto the chip 1 via the foam 22 to achieve the result depicted in FIG. 3.

The film sticker 31 may further include one or more pressure openings 34that extend through the membrane of the film sticker 31. The pressureopenings 34 allow the film sticker 31 to be porous so that air pressurecan pass therethrough. Thus, the pressure openings 34 serve to dissipatemechanical stress. In addition, it is possible to inject the foamthrough one or more of the pressure openings 34 to fill the pocket 32.

Similarly, the flexible carrier 2 may include one or more pressureopenings 35 that extend through the flexible carrier 2. The pressureopenings 35 are located in a region where the foam 22 is in contact withthe flexible carrier. It is possible to inject the foam through one ormore of the pressure openings 35 to fill the pocket 32. The pressureopenings 35 allow the flexible carrier 2 to be porous so that airpressure can pass therethrough. Thus, the pressure openings 35 serve todissipate mechanical stress.

While not shown, the flexible carrier 2 in FIG. 3 may further includeslits similar to slits 19 shown in FIG. 1.

FIG. 4 shows a cross-sectional diagram of a pressure sensor package 400according to one or more embodiments. Similar to the pressure sensorpackage 100 shown in FIG. 1, the pressure sensor package 400 includeschip 1 bonded to a flexible carrier 2 by bonding balls 3, with theexception that the bonding balls 3 are coupled to a back surface 14 ofthe chip 1 and the sensitive area of the MEMS element 12 faces away fromthe flexible carrier 2. The flexible carrier 2 may further include slits19.

In addition, the MEMS element 12 is arranged at the main surface 11 ofthe chip 1 and its exposed surface, including the sensitive area, iscompletely covered with the flexible protective material 13. The glob offlexible protective material 13 is further surrounded by a structuredmaterial 41 that is also disposed on the main surface 11 of the chip 1.Thus, the structured material 41 is disposed around a peripheral regionof the main surface 11, while the flexible protective material 13 andthe MEMS element 12 are disposed at an inner region of the main surface11.

The structured material 41 may be a structured synthetic resin, whichshould be sufficiently flexible to avoid the generation of excessivestress. A resin material that may be used in semiconductor processes ispolyemide. The resin provides an opening at an area around the MEMSelement 12, which may support a controlled deposition of the flexibleprotective material 13. Thus, the flexible protective material 13 isdispensed within the opening formed by the structured material 41.

Alternatively, the structured material 41 may be a structured siliconwafer or a structured glass wafer with a thermally adapted expansioncoefficient.

FIG. 5 shows a cross-sectional diagram of a pressure sensor package 500according to one or more embodiments. Similar to the pressure sensorpackage 400 shown in FIG. 4, the pressure sensor package 500 includeschip 1 bonded to a flexible carrier 2 by bonding balls 3, with theexception that the flexible protective material 13 completelyencapsulates the chip 1, including the MEMS element 12.

In addition, the pressure sensor package 500 includes a boundary frame51 that is bonding to the flexible carrier 2 with a bonding adhesive 52,such as glue or solder. The boundary frame 51 entirely surrounds aperiphery of the chip 1, and the flexible protective material 13 isdeposited globally over the chip 1 using the boundary frame 51 to retainthe flexible protective material 13 within a cavity that is formedbetween the walls of the boundary frame 51.

In FIGS. 4 and 5, it will also be appreciated that the flexible carrier2 may also be folded around the chip 1 to form a folded pocket aroundthe chip in a similar manner described with respect to FIGS. 2A-2C.Thus, FIGS. 4 and 5 may incorporate any of the features described inconjunction with FIGS. 2A-2C.

Similarly, in FIGS. 4 and 5, it will also be appreciated that the filmsticker 31 may be bonded to the flexible carrier 2 to enclose the chip 1within a pocket 32 in a similar manner described with respect to FIG. 3.Thus, FIGS. 4 and 5 may incorporate any of the features described inconjunction with FIG. 3.

FIG. 6 shows a top view of the pressure sensor package 100 shown inFIG. 1. As can be seen, the bonding balls 3 are connected to lead wires61. Also, slits or openings 19 formed in the flexible carrier 2 areshown. Multiple openings 19 surround a bonding region of the flexiblecarrier 2 where a respective bonding ball 3 is bonded thereto.

FIG. 7 shows a top view of the pressure sensor package 700 according toone or more embodiments. In particular, the pressure sensor package 700uses a regular PCB 72 made of, for example, FR4 or ceramic materialinstead of a flexible carrier. In addition, the PCB 72 includes stressrelieve springs 79 entrenched in the material of the PCB 72. The stressrelieve springs 79 are formed by milling grooves or channels in the PCB72. Each stress relieve springs 79 can be seen as two parallel channelsthat join together at the periphery of a corresponding bonding ball 3 toform one single integral channel.

Each channel wraps around a periphery of a corresponding bonding ball 3and extends outward towards a periphery of the PCB 72. A stress relievespring 79 may extend from a periphery of a corresponding bonding ball 3and extend to a periphery of the PCB 72 cattycorner from thecorresponding bonding ball 3. For example, one stress relieve spring 79wraps around the periphery of the bonding ball 3 located at the top leftcorner of the chip 1, wraps around a periphery of two adjacent sides ofthe chip 1 towards a lower right corner of the PCB 72.

It will be appreciated that the PCB 72 with stress relieve springs 79may be implemented in FIGS. 1, 3, 4, and 5, replacing the flexiblecarrier 2.

Although embodiments described herein relate to MEMS pressure sensors,and, in some cases capacitive pressure sensors, it is to be understoodthat other implementations may include other types of pressure sensorsor other types of MEMS devices or MEMS elements. In addition, althoughsome aspects have been described in the context of an apparatus, it isclear that these aspects also represent a description of thecorresponding method, where a block or device corresponds to a methodstep or a feature of a method step. Analogously, aspects described inthe context of a method step also represent a description of acorresponding block or item or feature of a corresponding apparatus.Some or all of the method steps may be executed by (or using) a hardwareapparatus, like for example, a microprocessor, a programmable computeror an electronic circuit. In some embodiments, some one or more of themethod steps may be executed by such an apparatus.

Further, it is to be understood that the disclosure of multiple acts orfunctions disclosed in the specification or claims may not be construedas to be within the specific order. Therefore, the disclosure ofmultiple acts or functions will not limit these to a particular orderunless such acts or functions are not interchangeable for technicalreasons. Furthermore, in some embodiments a single act may include ormay be broken into multiple sub acts. Such sub acts may be included andpart of the disclosure of this single act unless explicitly excluded.

Furthermore, the description and drawings merely illustrate theprinciples of the disclosure. It will thus be appreciated that thoseskilled in the art will be able to devise various arrangements that,although not explicitly described or shown herein, embody the principlesof the disclosure and are included within its spirit and scope.Furthermore, all examples recited herein are principally intendedexpressly to be only for pedagogical purposes to aid in theunderstanding of the principles of the disclosure and the conceptscontributed to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the disclosure, as well as specific examples thereof, areintended to encompass equivalents thereof. Thus, it is understood thatmodifications and variations of the arrangements and the detailsdescribed herein will be apparent to others skilled in the art.

Furthermore, the following claims are hereby incorporated into thedetailed description, where each claim may stand on its own as aseparate example embodiment. While each claim may stand on its own as aseparate example embodiment, it is to be noted that—although a dependentclaim may refer in the claims to a specific combination with one or moreother claims—other example embodiments may also include a combination ofthe dependent claim with the subject matter of each other dependent orindependent claim. Such combinations are proposed herein unless it isstated that a specific combination is not intended. Furthermore, it isintended to include also features of a claim to any other independentclaim even if this claim is not directly made dependent to theindependent claim.

What is claimed is:
 1. A semiconductor device, comprising: asemiconductor chip comprising a chip substrate and a MEMS element,wherein the chip substrate includes a first surface and a second surfacearranged opposite to the first surface, and wherein the MEMS element isdisposed at the first surface of the chip substrate and the MEMS elementincludes a sensitive area; at least one electrical interconnectstructure electrically connected to the first surface of the chipsubstrate; a chip carrier electrically connected to the at least oneelectrical interconnect structure; a flexible film provided over thesecond surface of the chip substrate to form a pocket in which thesemiconductor chip resides; and a compressible material arranged betweenthe second surface of the chip substrate and the flexible film.
 2. Thesemiconductor device of claim 1, wherein the flexible film is bonded tothe chip carrier in a region peripheral to the semiconductor chip. 3.The semiconductor device of claim 1, wherein the compressible materialencapsulates peripheral sides and the second surface of the chipsubstrate of the semiconductor chip.
 4. The semiconductor device ofclaim 1, wherein the compressible material fills a volume between thechip substrate and the flexible film.
 5. The semiconductor device ofclaim 4, wherein the compressible material fills a volume between thechip carrier and the flexible film.
 6. The semiconductor device of claim1, wherein the flexible film comprises at least one opening that isporous to air pressure.
 7. The semiconductor device of claim 1, whereinthe chip carrier comprises at least one opening that is porous to airpressure.
 8. The semiconductor device of claim 7, wherein thecompressible material extends, in a first volume, between the chipsubstrate and the flexible film and extends, in a second volume, betweenthe chip carrier and the flexible film such that at the compressiblematerial is in contact with the flexible film, with the second surfaceof the chip substrate, and with chip carrier, wherein the at least oneopening is arranged in a region where the compressible material is incontact with the chip carrier.
 9. The semiconductor device of claim 1,further comprising: a flexible protective material disposed between theMEMS element and the chip carrier.
 10. The semiconductor device of claim9, wherein the flexible protective material is bonded to the firstsurface of the chip substrate and encapsulates the sensitive area of theMEMS element.
 11. The semiconductor device of claim 9, wherein theflexible protective material is a silicone-based material.
 12. Thesemiconductor device of claim 9, wherein the sensitive area faces thechip carrier, and wherein pressure is applied directly to the flexibleprotective material such that the pressure is transferred through theflexible protective material to the MEMS element unchanged.
 13. Thesemiconductor device of claim 1, wherein the MEMS element is a pressuresensor.
 14. The semiconductor device of claim 1, wherein semiconductorchip is a bare die or a chip size package.
 15. The semiconductor deviceof claim 1, wherein semiconductor device is free from any molding. 16.The semiconductor device of claim 1, wherein the at least one electricalinterconnect structure is a bonding ball.
 17. The semiconductor deviceof claim 2, wherein: the MEMS element is a pressure sensor and thesensitive area is a pressure sensitive membrane that is separated fromthe chip carrier by a gap, and the flexible protective material extendsfrom the chip carrier to the pressure sensitive membrane, therebyfilling the gap between the pressure sensitive membrane and the flexiblecarrier such that the pressure sensitive membrane is encapsulated by theflexible protective material.
 18. A semiconductor device, comprising: asemiconductor chip comprising a chip substrate and a MEMS element,wherein the chip substrate includes a first surface and a second surfacearranged opposite to the first surface, and wherein the MEMS element isdisposed at the first surface of the chip substrate and the MEMS elementincludes a sensitive area; at least one electrical interconnectstructure electrically connected to the second surface of the chipsubstrate; a chip carrier electrically connected to the at least oneelectrical interconnect structure; a structured material disposed on thefirst surface of the chip substrate in a peripheral region of the firstsurface; and a flexible protective material bonded to the first surfaceof the chip substrate in an inner region that is circumscribed by thestructured material, wherein the flexible protective materialencapsulates the sensitive area of the MEMS element.
 19. Thesemiconductor device of claim 18, wherein the flexible protectivematerial is a silicone-based material.
 20. The semiconductor device ofclaim 19, wherein the structured material is a synthetic resin.
 21. Thesemiconductor device of claim 18, wherein pressure is applied directlyto the flexible protective material such that the pressure istransferred through the flexible protective material to the MEMS elementunchanged.
 22. The semiconductor device of claim 18, wherein the chipcarrier includes at least one opening that extends therethrough, each ofthe at least one opening being proximate to a bonding area of acorresponding one of the at least one electrical interconnect structure.23. The semiconductor device of claim 22, wherein a plurality ofopenings, including the at least one opening, surround a periphery theat least one electrical interconnect structure.
 24. The semiconductordevice of claim 23, wherein the at least one electrical interconnectstructure is a bonding ball.
 25. The semiconductor device of claim 18,wherein the chip carrier is a flexible carrier electrically that wrapsaround the semiconductor chip and extends over the first surface of thechip substrate such that a folded cavity is formed around thesemiconductor chip.
 26. The semiconductor device of claim 25, furthercomprising: a filling material, that is compressible and porous,disposed in the folded cavity and fills a gap between the first surfaceof the chip substrate and a portion of the chip carrier that extendsover the first surface of the chip substrate.
 27. The semiconductordevice of claim 18, further comprising: a flexible film provided overthe first surface of the chip substrate to form a pocket in which thesemiconductor chip resides; and a compressible material arranged betweenthe first surface of the chip substrate and the flexible film.
 28. Asemiconductor device, comprising: a semiconductor chip comprising a chipsubstrate and a MEMS element, wherein the chip substrate includes afirst surface and a second surface arranged opposite to the firstsurface, and wherein the MEMS element is disposed at the first surfaceof the chip substrate and the MEMS element includes a sensitive area; atleast one electrical interconnect structure electrically connected tothe second surface of the chip substrate; a chip carrier electricallyconnected to the at least one electrical interconnect structure; aboundary frame bonded to the chip carrier in a region peripheral to thesemiconductor chip, wherein the boundary frame defines a cavity in whichthe semiconductor chip is arranged; and a flexible protective materialthat at least partially fills the cavity such that peripheral sides andthe first surface of the semiconductor chip are entirely encapsulated bythe flexible protective material, wherein the boundary frame retains theflexible protective material within the cavity.
 29. The semiconductordevice of claim 28, wherein the chip carrier is a flexible carrierelectrically that wraps around the semiconductor chip and extends overthe first surface of the chip substrate such that a folded cavity isformed around the semiconductor chip.
 30. The semiconductor device ofclaim 29, further comprising: a filling material, that is compressibleand porous, disposed in the folded cavity and fills a gap between thefirst surface of the chip substrate and a portion of the chip carrierthat extends over the first surface of the chip substrate.
 31. Thesemiconductor device of claim 28, further comprising: a flexible filmprovided over the first surface of the chip substrate to form a pocketin which the semiconductor chip resides; and a compressible materialarranged between the first surface of the chip substrate and theflexible film.